Yes, this is either two males sorting out the pecking order, or else FAR MORE LIKELY a male (running) and female (jumping) and is a courtship/mating ritual. Notice the running bun is showing his scut (tail) very clearly. This is usually a show of aggression but is also seen in courtship. The female isn't willing at the beginning, but her jumps are becoming less and less high, and she is not showing her scut at all so is probably quite receptive to him.